Duke Energy Carolinas has filed a request with the N.C. Utilities Commission to increase its rates in North Carolina by about 12.6 percent. The change would take effect in January of 2010 if it is approved. The company estimates that the average residential bill, for 1,000 kilowatt-hours of electricity, would increase about $11 a month. The last general rate increase approved for Duke in North Carolina was in 1991. The utility company notes that in recent years rates have been lowered, and are currently below the national average.